Lateral Size and Thickness Dependence in Ferroelectric Nanostructures Formed by Localized Domain Switching

Ferroelectric nanostructures can be formed by local switching of domains using techniques such as piezo-force microscopy (PFM). Understanding lateral size effects is important to determine the minimum feature size for writing ferroelectric nanostructures. To understand these lateral size effects, we use the time-dependent-Ginzburg-Landau equations to simulate localized switching of domains for a PFM type and parallel-plate capacitor configurations. Our investigations indicate that fringing electric fields lead to switching via 90 deg domain wedge nucleation for thicker films while at smaller thicknesses, the polarization switches directly by 180 deg rotations. The voltage required to switch the domain increases by decreasing the lateral size and at very small lateral sizes the coercive voltage becomes so large that it becomes virtually impossible to switch the domain. In all cases, the width of the switched region extends beyond the electrodes, due to fringing.Comment: 21 pages, 11 figure

Interaction of Gold Nanoparticles in Barium Titanate Thin Films

A novel approach to control the grain size of oxide thin film materials has been investigated. Perovskite BaTiO3 shows interesting grain structures when deposited on gold predeposited, (111)-oriented, singlecrystal SrTiO3 substrates. Solid oxide films grow epitaxially on patterned seed layers and show variations in grain size relative to the films deposited on SrTiO3 directly.Comment: 14 pages, 4 figure

Blue lasing at room temperature in high quality factor GaN/AlInN microdisks with InGaN quantum wells

The authors report on the achievement of optically pumped III-V nitride blue microdisk lasers operating at room temperature. Controlled wet chemical etching of an AlInN interlayer lattice matched to GaN allows forming inverted cone pedestals. Whispering gallery modes are observed in the photoluminescence spectra of InGaN∕GaN quantum wells embedded in the GaN microdisks. Typical quality factors of several thousands are found (Q>4000). Laser action at ∼420nm is achieved under pulsed excitation at room temperature for a peak power density of 400kW/cm2. The lasing emission linewidth is down to 0.033nm

The giant planet orbiting the cataclysmic binary DP Leonis

Planets orbiting post-common envelope binaries provide fundamental information on planet formation and evolution, especially for the yet nearly unexplored class of circumbinary planets. We searched for such planets in \odp, an eclipsing short-period binary, which shows long-term eclipse-time variations. Using published, reanalysed, and new mid-eclipse times of the white dwarf in DP\,Leo, obtained between 1979 and 2010, we find agreement with the light-travel-time effect produced by a third body in an elliptical orbit. In particular, the measured binary period in 2009/2010 and the implied radial velocity coincide with the values predicted for the motion of the binary and the third body around the common center of mass. The orbital period, semi-major axis, and eccentricity of the third body are P_c = 28.0 +/- 2.0 yrs, a_c = 8.2 +/- 0.4 AU, and e_c = 0.39 +/- 0.13. Its mass of M_c sin(i_c) = 6.1 +/- 0.5 M_J qualifies it as a giant planet. It formed either as a first generation object in a protoplanetary disk around the original binary or as a second generation object in a disk formed in the common envelope shed by the progenitor of the white dwarf. Even a third generation origin in matter lost from the present accreting binary can not be entirely excluded. We searched for, but found no evidence for a fourth body.Comment: Accepted by A&

Diamond deposition on modified silicon substrates: Making diamond atomic force microscopy tips for nanofriction experiments

Fine-crystalline diamond particles are grown on standard Si atomic force microscopy tips, using hot filament-assisted chemical vapor deposition. To optimize the conditions for diamond deposition, first a series of experiments is carried out using silicon substrates covered by point-topped pyramids as obtained by wet chemical etching. The apexes and the edges of the silicon pyramids provide favorable sites for diamond nucleation and growth. The investigation of the deposited polycrystallites is done by means of optical microscopy, scanning electron microscopy and micro-Raman spectroscopy. The resulting diamond-terminated tips are tested in ultra high vacuum using contact-mode atomic force microscope on a stepped surface of sapphire showing high stability, sharpness, and hardnes

Inherited defects of piRNA biogenesis cause transposon de-repression, impaired spermatogenesis, and human male infertility

\ua9 The Author(s) 2024.piRNAs are crucial for transposon silencing, germ cell maturation, and fertility in male mice. Here, we report on the genetic landscape of piRNA dysfunction in humans and present 39 infertile men carrying biallelic variants in 14 different piRNA pathway genes, including PIWIL1, GTSF1, GPAT2, MAEL, TDRD1, and DDX4. In some affected men, the testicular phenotypes differ from those of the respective knockout mice and range from complete germ cell loss to the production of a few morphologically abnormal sperm. A reduced number of pachytene piRNAs was detected in the testicular tissue of variant carriers, demonstrating impaired piRNA biogenesis. Furthermore, LINE1 expression in spermatogonia links impaired piRNA biogenesis to transposon de-silencing and serves to classify variants as functionally relevant. These results establish the disrupted piRNA pathway as a major cause of human spermatogenic failure and provide insights into transposon silencing in human male germ cells

Here Comes the Bad News: Doctor Robot Taking Over

To test in how far the Media Equation and Computers Are Social Actors (CASA) validly explain user responses to social robots, we manipulated how a bad health message was framed and the language that was used. In the wake of Experiment 2 of Burgers et al. (Patient Educ Couns 89(2):267–273, 2012. https://doi.org/10.1016/j.pec.2012.08.008), a human versus robot doctor delivered health messages framed positively or negatively, using affirmations or negations. In using frequentist (robots are different from humans) and Bayesian (robots are the same) analyses, we found that participants liked the robot doctor and the robot’s message better than the human’s. The robot also compelled more compliance to the medical treatment. For the level of expected quality of life, the human and robot doctor tied. The robot was not seen as affectively distant but rather involving, ethical, skilled, and people wanted to consult her again. Note that doctor robot was not a seriously looking physician but a little girl with the voice of a young woman. We conclude that both Media Equation and CASA need to be altered when it comes to robot communication. We argue that if certain negative qualities are filtered out (e.g., strong emotion expression), credibility will increase, which lowers affective distance to the messenger. Robots sometimes outperform humans on emotional tasks, which may relieve physicians from a most demanding duty of disclosing unfavorable information to a patient